I got a Namco Museum invite.
You download and install it and it's a game in it's own right, it's not a version of Home. When you play games you get "rewards" and the next time you log into home you get these rewards.
For example if you complete a level on Pacman you get a pacman t-shirt. Same on Dig-dug you get an ornament for your flat.
The games are:
Pacman
Dig-Dug
Galaga
Xevious
So far I have unlocked a few T-shirts, some shorts, an ornament for my flat and a Galaga arcade cabinet for my flat.
Don't get too excited though, it's only the clothes that you'll be able to use with your EU account, you can put the arcade cabinet and the ornament in your flat but next time you log in they get removed. Also if you try and play the arcade cabinet it says you need to use your jap account.
So basically if you get a code you can download Namco Museum, install it and it will show up in your games list just like other games/demos and you can play it with any account.
Hope that helps, any other questions?
(no, I don't want to "share" it, too scared about my account to do that lol)